Apparatus and method for testing drape of a fabric



Aug. 2, 1955 w, HAMBURGER ET AL 2,714,328

APPARATUS AND METHOD FOR TESTING DRAPE OF A FABRIC Filed July 28, 1951 2 Sheets-Sheet 1 Fig.1

5 liNVENTOgSp/(j g 1955 w. J. HAMBURGER ET L 2,714,323

APPARATUS AND METHOD FOR TESTING DRAPE OF A FABRIC Filed July 28, 1951 2 Sheets-Sheet 2 IN EN 0R5 arr/v69 Patented Aug. 2, 1955 APPARATUS AND METHQD FOR TESTING DRAPE A FABREC Walter J. llllarnhurger, Dedham, and Clinton L. Cummings, Naticlr, Mass, assignors to Fabric Research Laboratories, hm, Eastern, Mass, a corporation of Massachusetts Application July 28, 1951, Serial No. 239,172

Claims. {CL 88-14) This invention relates to the testing of textile materials and more particularly to an apparatus and method for testing the drape of a textile material.

Drape and drapability" are terms for that property of textile materials which allows a fabric to orient itself into graceful folds or pleats when acted upon by the force of gravity, for instance, when a cape is draped over the shoulders or a skirt around the hips of the wearer. The textile industry has long realized the importance of the drape of a textile material and the desirability of obtaining a fuller understanding of such property. The lack of a suitable measuring technique, has, however, been a real barrier to the further investigation of drape, and the industry has continued to rely on the opinion of experts in regard to such property of a textile fabric. Such opinion, moreover, varied from expert to expert and was not reproducible even with the same textile material.

Some attempts have been made to measure drape in a reproducible manner by determining the bending properties of a fabric. We have found, however, that such tests do not properly determine the drape of a fabric since they are incapable of differentiating between drape and paperiness, i. e., it is possible to select a piece of paper and a fabric both of which have the same bending properties, yet the paper will not drape as well as the cloth. For instance, childrens party costumes are often made of crepe or tissue paper; however, regardless of how flexible the paper may be, it does not have the same appearance as cloth, it is seldom graceful. in short, it does not drape.

We have found that in order properly to determine the drape of a textile fabric, by which term we mean to include any flexible sheet material used as a textile material, it is essential that the fabric to be evaluated be so supported that it will freely orient itself by multiplanar deformation of the fabric involving buckling to form folds or pleats. Under such conditions, a fabric having good drape will form graceful pleats in a number of places as well as directions, whereas a papery material will either bend in but one place and one direction to form a simple curved plane or will form sharp un attractive folds. Thus, to evaluate the drape of a textile or other sheet material, we support preferably in a horizontal plane a sample of the fabric in its central portion only, the edges around the entire periphery of the sample being entirely unsupported, such fabric sample for prac* tical reasons preferably being circular and supported in its central concentric portion, although other configurations could well be used. Under such conditions, the unsupported edges of the sample will be free to drape downwardly in a manner determined by the drapability of the fabric, forming one or more pleats or folds depending upon the draping characteristics of the fabric. The amount of drape of the freely downwardly draped edge, as compared to that of the undraped sample, may then be measured by progressively determining the projected horizontal radial distance from the supported central portion of the sample to the draped peripheral edge of the sample. Thus, if a line corresponding to the draped peripheral edge of the sample projected into a horizontal plane is traced or otherwise reproduced, for instance by presenting the draped edge to a scanning device movable relatively with respect to such edge to follow it as hereinafter more fully explained, such line will he found to enclose an irregular area (Fig. 2), such area generally being symmetrical in the case of a fabric having good draping qualities. We have further found that a numerical figure-the drape coeflicientrelated to the drape of the fabric of the sample may be derived by comparing the annular area of the undraped sample, that is the area between the supported and unsupported portions of the sample with the irregular vertically projected area of the centrally supported draped sample. Under standard conditions, such as by using a standard disk support and a standard size of circular fabric sample, the drape coefiicient of a fabric as determined by our novel method and apparatus is reproducible and has otherwise been found to be an entirely satisfactory method of determining the drape of a fabric without the necessity of relying upon expert opinion.

In order more fully to explain our novel method and apparatus, reference is made to the following drawings,

in which:

Fig. l is a diagrammatic view of a preferred embodiment of a novel apparatus for determining the drapability of a textile fabric,

Fig. 2 is an illustration of a projected area of a circular centrally supported draped fabric sample,

Fig. 3 is a schematic view of certain portions of the apparatus of Fig. 1, and

Fig. 4 is a diagrammatic view of a modification of of the apparatus of Fig. 1.

Referring now to Fig. 1, we have provided a novel apparatus by which the drape of a sample of textile fabric may be easily and quickly measured. In such apparatus, the circular fabric sample 2 is supported between a pair of disks 1t and 12 of the same diameter, such sample being of greater diameter than that of said disks and being arranged concentrically with respect thereto so that the peripheral edge of the sample is not directly supported by the disks and is free to drape downwardly under the influence of gravity. The disks 1t) and "12 are supported on vertical shaft 14 and may be rotated in a horizontal plane by motor through sprocket 16, chain 17 and sprocket 13 on the vertical shaft 19 of motor 20. in order continuously to determine the radial distance between the draped edge 4 of the sample and the edge of disks 1t) and 12, we have provided a follower mechanism which scans the draped sample and automatically and continuously positions itself at the draped edge 4 of the sample 2 as the sample is rotated by motor 20. Such mechanism includes a follower head 22 mounted on a pair of tracks 24 for movement radially of disks 1t) and 12 and sample 2. Head 22 is moved back and forth normally to the axis of shaft 14 to follow the draped edge 4 by a reversible two phase follower motor 26 which drives a horizontally extending belt 28 which is at a point in one light thereof attached to said head 22. Follower motor 2* is controlled to move head 22 toward and away from the center of disks fill and 12 in response to the draped edge 4 of sample 2 by a photoelectric scanning unit including a photocell 39 mounted on one end of said head and a scanning lamp 31 on the other end of said head, said lamp 31 providing a narrow vertically directed beam of light 32 focused on cell 39. Suitable collimating means (not shown) is provided for the unit as is well known in the art. The cell 30 and lamp 31 being disposed on opposite sides of the draped sample, the scanning beam 32 will thus be in a position to intercept the draped edge of said sample. To continuously position the head 22 so that the scanning beam 32 intercepts the sample at the edge 4 thereof, a comparison lamp 34 and comparison photocell 36 are used, the two photocells and 36 being electrically bucked against each other. The brightness of the lamp 34 normally is adjusted by any suitable means such as variable resistance 33 until the light falling on the comparison cell ,36 is approximately equivalent to the light which reaches the scanning cell 39 when the beam 32 is intercepted, preferably cut in half, by the edge of the sample. Under such conditions, since the D. C. output voltages of the two cells are bucked against one another, no voltage will appear; however, when the beam of light 32 is not intercepted by the edge 4 of the sample, a voltage equal to the difference between the output voltages of each of the cells will appear at their confined output; Such voltage, by means of a suitable amplifier 38, may be used to control the two phase follower motor 26 to restore the follower head 22 to a position in which the beam 32 will be intercepted by edge 4.

Fig. 3 illustrates suitable electrical circuits used for operating motor 26 in response to the beam of light 32, including the circuit of the amplifier 38 for controlling one winding of two phase motor 26, such amplifiers being generally well known. Briefly, it includes a D. C. chopper 42 operated by the A. C. supply voltage for chopping the control voltage output from the photocells to provide a suitable alternating voltage at the secondary of transformer 44 and a vacuum tube amplifier for amplifying the alternating signal voltage. The output of the amplifier is used to provide a voltage which appears across one winding 46 of the two phase motor 26, the other winding 48 of said motor being connected to the supply line, the phase diftlerence between such two voltages acting to operate said motor. Thus, as the illumination is increased or decreased as a result of the rotation of the sample 2, the output voltage of the two photocells as fed to the D. C. chopper 42 will create an alternating signal voltage in the secondary of transformer 44, such alternating voltage being in synchronism with the supply voltage and differing in phase therefrom. The signal, after being amplified in the usual manner by the amplifier 38 is applied to one winding 46 of two phase motor 26, and, depending upon the amplitude difference between such signal voltage and the supply voltage applied to the other Winding 48 of motor 26, will move head 22 to restore follower head 22 by moving said head toward or away from the disks 1i) and 12 to a position in which the scanning beam 32 is intercepted by edge 4 of sample 2. Head 22, then, will measure progressively the horizontal radial distance between the draped edge 4 of the sample 2 and the edge of the disks 1'!) and 12 as the sample is revolved.

Since it is desirable to record the distance measured by the follower head 22, in order progressively to record the projected drape diagram and the projected annular area of the draped sample, we have provided a tracing device including a chart turntable on motor shaft 19, rotating synchronously with disks 10 and 12 and sample 2, and a follower arm 23 attached to follower head 22 and extending radially of both disks lit and 12 and of chart turntable 40, a pen 42 being mounted on said arm at the same distance from the axis of chart turntable 413 as that of the light beam 32 from the axis of disks 1!) and 12. Pen 42 will, then, as sample 2 and chart turntable 4%) are rotated, move toward and away from the center of turntable it? as follower head 22 moves normal to said disks to follow the edge 4 of the sample, thus tracing preferably on a circular chart of a usual type on the chart turntable 40 during its course of one revolution of the sample, a line 41 corresponding to the draped peripheral edge 4 of sample 2 vertically projected into a horizontal plane. The tracing thus produced may be used to determine the projected annular area of the draped sample for comparison with that of the undraped sample to determine the drape coefficient of the sample, and the tracing may be retained as a permanent record of the experiment.

Although the drape coefiicient may be determined from the tracing, as above described, we have found it expedient to determine the projected annular area simultaneously with the making of the tracing, and thus we provide with the apparatus of Fig. l a novel integrating device which will progressively measure the irregular projected area of the draped sample, the annular area then being determinable by a simple subtraction of the known area of disks 10 and 12 and may thus provide without computation a reading of the total annular projected area upon completion of a single revolution of the draped sample. Referring now to Fig. 4, our novel integrating device for progressively measuring the irregular area includes a first disk 50 mounted for rotation about an axis and driven through sprocket 51 from sprocket 52 on motor shaft 19. A pair of balls, upper ball 55 and lower ball 56, suitably retained in frictional driving contact with one another at all times, are arranged to be moved by follower head 22 radially of disk 50, said balls conveniently being mounted on an integrator arm 54 attached to follower arm 23 and movable therewith so that the balls will move radially of disk 56 in response to the movement of said follower head. The lower ball 56 remains at all times in frictional driving contact with said disk 50, while upper ball 55 is in frictional driving contact at all times with a cylinder 58 the axis of'which extends radially of the disk 50. The rate of rotation of cylinder 58 as driven by disk 50 through balls 55 and 56 is dependent upon the radial distance of the point of contact of lower ball 56 from the axis of disk 50, the balls 55 and 56 being free to be moved toward and away from the axis of disk 50 since the lower ball 56 will roll along disk Sit, and the upper ball along cylinder 58 parallel to the axis thereof, while the balls will simultaneously roll in contact with one another.

To directly measure the irregular area, we have provided a second ball and disk integrator similar to the first as above described, having a second disk 60, a second pair of balls 62 and 63 and a second cylinder 64. The second disk 66 is driven by first cylinder 58 through bevel gears 66, and the balls 62 and 63 are mounted on integrator arm 54 for radial movement on second disk 60 in response to the movement of follower head 22 in the same manner as the first pair of balls 55 and 56. Since second disk 6 1' is driven at a speed dependent upon the radial distance of the point of contact of the first pair of balls 55 and 56 with the axis of disk 50, and since the second pair of balls 62 and 63 will drive said second cylinder 64 at a speed dependent upon the radial distance of the point of contact of one of said balls with respect to the axis of the second disk 60, the rotation of the second cylinder 64 will be dependent upon the square of the radius of the follower beam 32 from the axis of the sample. Thus, the irregular projected area may be read directly at the completion of a single revolution of sample 2 on a counter 7% of a type which multiplies its input revolutions by a given number such as pi, and the annular area determined by subtracting the known disk area, preferably by a suitable initial setting of the counter.

Thus it will be apparent that we have provided a novel method and apparatus for measuring the drape of a textile fabric, as well as an integrator for use with such apparatus for measuring the projected irregular annular area of a draped sample of fabric. Various modifications of our novel method and apparatus within the spirit of our invention and the scope of the appended claims will occur to those skilled in the art.

We claim:

1. Apparatus for testing the drape of a fabric including sample supporting means supporting in a horizontal plane a central portion only of a fabric sample whereby the peripheral edge portion of said sample is not directly supported by said sample supporting means and is free to drape downwardly, follower means mounted for movement toward and away from said sample supporting means and adapted to follow the draped peripheral edge of said sample and determine the horizontal distance between the draped peripheral edge of said sample and said sample supporting means, and means for rotating said sample supporting means and said follower means relatively to one another whereby said follower means will progressively determine said distance.

2. Apparatus as claimed in claim 1 in which said supporting means includes a disk means supporting in a horizontal plane a central concentric portion of a circular fabric sample of greater diameter than that of said disk means, and in which said follower means is adapted to move radially of said disk means to follow the draped peripheral edge of said sample and determine the horizontal radial distance between the draped peripheral edge of said sample and the edge of said disk means.

3. Apparatus for testing the drape of a fabric including sample supporting means supporting in a horizontal plane a central portion only of a fabric sample whereby the peripheral edge portion of said sample is not directly supported by said sample supporting means and is free to drape downwardly, follower means mounted for movement toward and away from said sample supporting means and adapted to follow the draped peripheral edge of said sample and determine the horizontal distance between the draped peripheral edge of said sample and said sample supporting means, means for rotating said sample supporting means and said follower means rela tively to one another whereby said follower means will progressively determine said distance, and recording means actuated by said follower means for progressively recording said distance.

4. Apparatus as claimed in claim 3 in which said recording means includes means for tracing in a horizontal plane a line corresponding to the draped peripheral edge of said sample projected into said plane.

5. Apparatus as claimed in claim 3 in which said recording means includes integrating means for progressively measuring the horizontally projected area between the draped peripheral edge of said sample and said sample supporting means.

6. A method of testing the drape of a fabric including supporting a sample of fabric by supporting in a horizontal plane a central portion only of said sample the peripheral edge portion of said sample being free to drape downwardly, and determining the projected area of said sample, a drape coefficient of said fabric being defined by comparing the irregular vertically projected annular 6 area of the draped sample with the annular area of the undraped sample.

7. A method of testing the drape of a fabric including supporting a circular sample of fabric by supporting in a horizontal plane a central concentric portion only of 1 said sample the peripheral edge portion of said sample being free to drape downwardly, and progressively determining the horizontally projected radial distance of the peripheral edge of said sample from the centrally supported portion of said sample, a drape coefficient of said fabric being defined by comparing the irregular vertically projected annular area of the draped sample with the annular area of the undraped sample.

8. A method of testing the drape of a fabric including supporting a sample of fabric by supporting in a horizontal plane a central portion only of said sample the peripheral edge portion of said sample being free to drape downwardly, and tracing in a horizontal plane a line corresponding to the horizontally projected draped peripheral edge of said sample, the draping characteristics of said fabric being determined by the number and shape of the folds as indicated by said line.

9. A method of testing the drape of a fabric including supporting a circular sample of fabric by supporting in a horizontal plane a central concentric portion only of said sample the peripheral edge portion of said sample being free to drape downwardly, and tracing in a horizontal plane a line corresponding to the horizontally projected draped peripheral edge of said sample, the draping characteristics of said fabric being determined by the number and shape of the folds as indicated by said line.

10. A method of testing the drape of a fabric including supporting a circular sample of fabric by supporting in a horizontal plane a central concentric portion only of said sample the peripheral edge portion of said sample being free to drape downwardly, and determining the projected area of said sample, a drape coeflicient of said fabric being defined by comparing the irregular vertically projected annular area of the draped sample with the annular area of the undraped sample.

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